Downhole operations and the handling of downhole well tools in completed wells has always presented a certain challenge, especially when working in wells having a natural pressure that exceeds atmospheric pressure necessitating the containment of the well at all times. Another challenge has been the maintenance of well bores which pass through production zones that are not well suited to continuous production. For example, production zones which yield both water and oil may require frequent repositioning of production tubing in order to recover oil efficiently. Another example is production zones which produce crude oil high in waxy compounds or asphaltines or laden with salts which tend to plug casing perforations and therefore require frequent treatment to maintain an economic flow of hydrocarbon. To date, the maintenance of such wells has proven time-consuming and expensive. For example, in wells which produce both oil and water and have a mobile water/oil interface, the production of oil gradually decreases over time until only water is produced from the well. Relocation of the bottom end of the production tubing string is then required to recommence oil production. The relocation of the tubing string typically involves at least the following steps:
1) killing the well with kill fluid or running in plugs so the wellhead can be removed; PA1 2) removing the wellhead; PA1 3) installing BOPs; PA1 4) pulling the production tubing; PA1 5) cleaning the casing; PA1 6) running in a cement retainer; PA1 7) cementing off the borehole at the current water/oil interface; PA1 8) perforating the casing above the cement; PA1 9) running back the production tubing; PA1 10) replacing the wellhead; and PA1 11) removing the drilling mud to restore production. PA1 first and second telescopingly interconnected tubular sections having opposite ends adapted for connection to the conduit; and PA1 a latch point for connection of a member for extending or retracting the telescoping joint, the latch point being disposed internally of the telescoping joint so that the member can be inserted through the telescoping joint and connected to the latch point to controllably extend or retract the telescoping joint from one end of the conduit. PA1 a tubing string having a top end and a bottom end; PA1 at least one pair of sealing means for engaging an inner periphery of the casing of the cased well bore in a fluid tight seal, the sealing means being attached to the tubing string in a spaced-apart relationship for providing at least one isolated fluid zone when the tubing string is inserted in the cased well bore and the sealing means are in sealing engagement with the casing; PA1 means for enabling fluid communication between the at least one isolated fluid zone in the well bore and an interior of the tubing string; PA1 a telescoping joint for permitting axial displacement of a bottom section of the tubing string with respect to a top section thereof, the telescoping joint being located above the at least one pair of sealing means; and PA1 means for permitting the bottom section of the tubing string to be displaced with respect to the top section, PA1 whereby when the tubing string is inserted in a well bore and the top section of the tubing string is attached to a tubing hanger or directly to the wellhead, the bottom section of the tubing string may be axially displaced to reposition the isolated fluid zone in the cased well bore. PA1 a) locating a position of the production zone, a position of interfaces between the at least two fluids and a distance between top and bottom surfaces of the fluid of interest; PA1 b) assembling a tubing string in the cased well bore, the tubing string including: PA1 c) attaching a top end of the tubing string to a tubing hanger or a wellhead at a top of the casing; PA1 d) positioning the pair of spaced-apart sealing means so that they are respectively located approximate the top and bottom surfaces of the fluid of interest by axially displacing the bottom section of the tubing string using the telescoping joint, if required; PA1 e) producing the fluid of interest from the isolated fluid zone in the well bore through the tubing string; and PA1 e) periodically adjusting a position of the bottom section of the tubing string to maintain at least one of the sealing means at the interface between the at least two fluids so that predominantly only the fluid of interest communicates with the isolated fluid zone.
It is not difficult to appreciate that there is a need for a more efficient and less costly system for producing oil from such wells.
Methods have been invented for producing hydrocarbons from water-bearing formations. One such method is described in U.S. Pat. No. 5,443,120 which issued on Aug. 22nd, 1995 to Howell. This patent describes a method for improving the productivity of a well by separating and disposing of at least a portion of the water which is produced from a subterranean producing formation. The water is permitted to separate from the produced fluids under the influence of gravity while in the well bore. The separated water is disposed of without removing it from the well bore by flowing it into a subterranean disposal formation which has a pressure less than that of the producing formation. In order to accomplish this, the well is completed with an inclined well bore which aids in the gravity separation of the water from the produced hydrocarbons. A problem with this method is that it requires a low pressure disposal formation located beneath the producing formation. Besides, the inclined well bore is problematic unless there is adequate natural pressure to produce oil to the surface since the inclination of the well bore makes connecting pumping equipment or the like inconvenient.
Another challenge in the industry is the "barefoot" completion of wells. Barefoot completions are desirable if losing drilling mud into a production zone is likely to damage the zone or the zone contains toxic gases such as sour gas. Drilling contractors frequently do not complete such wells. Rather, they drill down and case the well to an area just above the production zone and leave the bore to be completed after a casing flange and blowout preventers are installed. A completion rig is brought in and the last few meters into the production zone are drilled. The bottom of the bore is usually not cased, hence the name "barefoot". If barefoot completion is effected in a "critical zone" known or suspected to contain toxic gas, regulations normally require many precautionary measures. For example, gas ignition equipment must be on standby, manned, downwind monitors must be on site and at least one safety person must be on location until the completion is finished. There therefore exists a need for a simpler, more cost-effective way of completing wells in critical zones.
It is known in the prior art to use a torque-transmitting expansion joint to permit a selectively adjustable extent of axial contraction in production tubing to absorb temperature-produced variations in length of a space-out section or dimensional differences between the planned and actual location of a surface hanger with respect to a downhole tubing hanger. Such apparatus is described in U.S. Pat. No. 4,403,654 which issued on Sep. 13, 1983 to Haynes. This expansion joint is designed to permit limited axial movement of a tubing string in which it is installed while permitting rotational torque to be transmitted through the joint. While this expansion joint is useful in its intended application, it does not contribute to a solution to the problems of selective production or well bore completions described above. Nor does it contribute a solution for the relocation of downhole tools without the disconnection of a tubing string from the wellhead.
It is therefore desirable to provide an apparatus for use in a conduit in a well bore such as a tubing string for supporting downhole well tools to permit the downhole well tools to be axially displaced in the well bore without disconnecting the conduit from the wellhead.